Cisco CCNP Enterprise 300-410 Questions & Answers

• Question 611:

  Which command should be executed on all ABRs in an area to configure it as a totally stubby area?

  A. Router(config-router)# area process-id stub [no-summary]

  B. Router(config-router)# area area-id [no-summary] stub

  C. Router(config-router)# area area-id stub [no-summary]

  D. Router(config-ospf)# area router-id [no-summary] stub

  Correct Answer: C

  The correct syntax for the area stub command to configure a totally stubby area is shown below:

  Router(config-router)# area stub [no-summary]

  Note that the optional no-summary keyword is used only on area border routers (ABRs) to block summary link advertisements into the stub area. This option creates a totally stubby area. All internal routers in the area need only the stub

  keyword without the no summary keyword.

  It is very important to configure the command consistently on all routers within the area. OSPF sends its stub status (on or off) in its hello packets. If two neighbors have conflicting stub status, for example, if one indicates that a stub is present

  and the other indicates that no stub is present, they will not form an adjacency, and you end up with no OSPF communication over that link.

  The other options are either using incorrect syntax or being executed at an incorrect prompt. The area stub command should be executed at the OSPF router configuration prompt.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify network types, area types, and router types

  References:

  Cisco > Home > Support > Technology Support > IP Routing > Design > Design Technotes > What Are OSPF Areas and Virtual Links? > What Are Areas, Stub Areas, and Not-So-Stubby Areas? Cisco > Cisco IOS IP Routing: OSPF

  Command Reference > area stub

• Question 612:

  You have configured a BGP network with several routers in the same autonomous system (AS). There are three possible routes from router A to router B in the network. The following conditions exist: All three routes have the same weight All three routes were originated locally through the use of the network command The bgp default local-preference 50 command is executed for all three routes All three routes have different lists of AS through which they travel

  Which of the following parameters is used to select the best path among the three routes?

  A. Weight

  B. MED

  C. LOCAL_PREF

  D. AS_Path

  Correct Answer: D

  The AS_Path parameter is used to select the best path among the three routes. To select the best path from router A to router B, BGP analyses various BGP attributes that are set during the configuration of the network. The key BGP attributes and the order in which they are checked are as follows:

  1.

  Weight - highest weight is selected

  2.

  LOCAL_PREF - highest LOCAL_PREF is selected

  3.

  Locally originated routes - local routes are selected

  4.

  AS_PATH - shortest AS_PATH is selected

  5.

  Origin type - lowest origin type is selected

  6.

  Multi-exit Discriminator (MED) - lowest MED is selected

  Because the weight attribute is same for all three routes, BGP checks the value of the LOCAL_PREF attribute. However, this attribute is also same for the three routes because the bgp default local-preference 50 command was executed for

  the three routes, which sets the value of the LOCAL_PREF attribute to 50 for those routes.

  BGP then checks whether any of the routes were locally originated using either the network or aggregate commands. As stated in the scenario, all three routes were locally originated with the network command during BGP configuration.

  Consequently, BGP analyzes the value of the AS_PATH attribute. This attribute refers to a list of AS numbers that are traversed by a particular route. The route with the shortest AS_PATH is selected as the best path.

  The weight attribute is not used to select the best path in this case. The weight attribute for all three routes is the same. If this attribute were different for the three routes, then the route with the highest weight would be considered the best

  path.

  The MED attribute is not used to select the best path in this case. The MED, or multi-exit discriminator, specifies the route into an AS that has more than one entry points. A route with the lowest MED is selected as the best path. However, in

  this case, the MED attribute is not considered because the AS_PATH attribute is different for the three routes. If the AS_PATH attribute for the three routes were the same, then the MED attribute would have been considered. The

  LOCAL_PREF attribute is not used to select the best path. The LOCAL_PREF attribute is checked if the weight attribute for the routes is same. The LOCAL_PREF attribute refers to the local preference, which specifies the route that has

  preference to exit the AS for a given destination network. The route with the highest LOCAL_PREF value is selected as the best path. However, the bgp default local-preference 50 command was executed for all three routes. Hence, this

  attribute is not considered to select the best path between the BGP routers A and B.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Explain BGP attributes and best-path selection

  References:

  Cisco > Home > Support > Technology Support > IP > IP Routing > Design > Design TechNotes > BGP Best Path Selection Algorithm

• Question 613:

  You instructed your assistant to configure redistribution of OSPF routes into EIGRP on Router 9. The routes are not being advertised to EIGRP and you are troubleshooting the problem. The EIGRP process ID is 100 and the OSPF process ID is 20. When you ask your assistant what commands were executed, you are shown the following:

  Router9(config)# router eigrp 100 Router9(config-router)# redistribute ospf 20

  What is the problem?

  A. no metric was configured

  B. the process IDs are incorrect

  C. the redistribute command is executed at the interface configuration prompt

  D. the redistribute command is executed at the global configuration prompt

  Correct Answer: A

  The problem is that the metric was not configured. Some routing protocols require that a metric be provided for the redistributed routing protocol or route redistribution will not occur successfully. RIP and EIGRP both require that a metric be

  provided. IS-IS and OSPF do not have this requirement.

  When you redistribute traffic into EIGRP without specifying a metric, then the default metric applied is zero, the route will be treated as unreachable, and the route will not be advertised. The addition of the metric parameter as shown below

  would solve this issue:

  Router9(config)# router eigrp 100

  Router9(config-router)# redistribute ospf 20 metric 10000 100 255 1 1500

  In this example, 1000 is the bandwidth, 100 is the delay, 255 is the reliability, 1 is the load, and 1500 is the MTU.

  The process IDs are correct in the original scenario, and the command was executed in the correct context.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify redistribution between any routing protocols or routing sources

  References:

  Cisco > Home > Support > Technology Support > IP > IP Version 6 > Configure > Configuration Examples and Technotes > Redistributing Routing Protocols

• Question 614:

  Examine the following output of the show ip ospf interface command.

  

  What would be the effect of executing the auto-cost reference bandwidth 2000 command on Router43 in router OSPF mode?

  A. the cost of the Serial interface would increase to 20

  B. the cost of the FastEthernet interfaces would increase to 2000

  C. the cost of the Serial interface would increase to 647

  D. the cost of the FastEthernet interfaces would increase to 20

  Correct Answer: D

  If the auto-cost reference bandwidth 2000 command is executed in router OSPF mode it will result in a cost to the FastEthernet interfaces of 20. The formula for arriving at the cost is: reference bandwidth / interface bandwidth = cost

  The default reference bandwidth for FastEthernet is 100 Mbps. If the reference bandwidth is set at 2000 Mbps using the auto-cost reference command, and the FastEthernet interface has a bandwidth of 100 Mbps, the resulting cost is 20

  (2000 / 100 = 20).

  The auto-cost reference bandwidth command is executed in router OSPF mode to affect all interfaces. Alternatively, the cost of each interface can be set separately with the ip ospf cost command issued in interface configuration mode. The

  two commands can also be used in combination: you can set all interfaces with the auto-cost reference bandwidth command, and then set a single interface to a different cost with the ip ospf cost command.

  The command would not result in the cost of the Serial interface increasing to 20 or to 647. With a reference bandwidth of 2000 Mbps and interface bandwidth of 1544 kbps (the default bandwidth of a serial interface), the resulting cost would

  be 1294.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify OSPF path preference

  References:

  Cisco > Home > Support > Technology Support > IP > IP Routing > Technology Information > Technology White Paper > OSPF Design Guide > OSPF Cost Cisco > Cisco IOS IP Routing: OSPF Command Reference > show ip ospf interface

  Cisco > Cisco IOS IP Routing: OSPF Command Reference > auto-cost

• Question 615:

  Which of the following IPv6 addresses correctly represent the shortened version of the IP address 2031:0000:0000:130F:0000:0000:876A:130B? (Choose two.)

  A. 2031::130F::876A:130B

  B. 2031::130F:0:0:876A:130B

  C. 2031:0:130F::876A:130B

  D. 2031:0:0:130F::876A:130B

  Correct Answer: BD

  2031:0000:0000:130F:0000:0000:876A:130B can be shortened to either 2031::130F:0:0:876A:130B or 2031:0:0:130F::876A:130B.

  IPv6 addresses are written in 16-bit hexadecimal number fields separated by a colon (:). There are a total of eight 16-bit fields, making each IPv6 address a total of 128 bits. The hexadecimal letters are NOT case sensitive.

  You can shorten an IPv6 address by removing the leading zeros in any address field. You can only remove zeros that are the first character in an address field. For example, FFC0:02C0: is the same as FFC0:2C0:.

  However, FFC0:8020 is not the same as FFC0:802:.

  If a 16-bit address field contains all zeros, then it can be represented by a single zero. For example, FF80:0000: is the same as FF80:0:.

  You can use double colons (::) to represent successive address fields of zeros. An address parser can determine the number of missing fields and then insert the proper number of zeros to complete the address. For example,

  FF80:0000:0000:0000:0000:0000:0000:0001 is the same as FF80::1, and 0000:0000:0000:0000:0000:0000:0000:0001 could be written as ::1. However, you can only have one set of double colons (::) in an address; therefore,

  FF80:0000:0000:0CB0:0000:0000:0000:0001 cannot be written as F80::0CB0::1.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Identify IPv6 addressing and subnetting

  References:

  Cisco > IPv6 Addressing and Basic Connectivity Configuration Guide > IPv6 Addressing and Basic Connectivity

  Cisco > IPv6 Addressing at a Glance (PDF)

• Question 616:

  Examine the diagram below:

  

  Based on the diagram and the following partial output from Router R2, which networks will be present in the routing table of Router R1?

  

  A. 192.168.5.0

  B. 10.0.0.0

  C. 172.50.0.0

  D. 192.168.5.0 and 10.0.0.0

  Correct Answer: D

  The routes that will be present in Router R1 are 192.168.5.0 and 10.0.0.0. According to the output, only the route from EIGRP 55 will be redistributed to EIGRP 200. Therefore, the 10.0.0.0 network will be advertised to Router R1 from Router

  R2 and the 192.168.5.0 network, which is present in the routing table of Router R2, will be advertised to Router R1.

  The 192.168.5.0 network alone would not be correct. The 10.0.0.0 network will be present as well.

  The 172.50.0.0 network will not be present because Router 2 is not configured with a redistribution statement for that network. The required statement would be redistribute ospf 1.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify redistribution between any routing protocols or routing sources

  References:

  Cisco > Home > Support > Technology Support > IP > IP Version 6 > Configure > Configuration Examples and Technotes > Redistributing Routing Protocols

• Question 617:

  Refer to the following diagram of an OSPF network.

  

  Which of the following routers generate network link advertisements (NLA)? (Choose all that apply.)

  A. R3

  B. R4

  C. R7

  D. R8

  E. R9

  F. R13

  Correct Answer: AE

  The R3 and the R9 routers in the scenario generate network link advertisements (NLA). An NLA or a Type 2 LSA is generated only by the designated router (DR) of a segment. Type 2 LSAs are generated only for those networks in which a

  DR has been selected. A DR is a router that has the highest OSPF priority on a segment. Until there are two OSPF routers on the segment, no Type 2 LSAs will be generated.

  Type 2 LSAs are flooded in the area that contains the network segment with the DR. These advertisements are used by the DR to represent the routers that are connected to the network. This type of LSA is sent to those routers that belong to

  the same network as the DR. Therefore, in this case, Type 2 LSAs are generated by the R3 and the R9 routers. R3 sends the LSAs to R1, R2, and R4, while R9 sends LSAs to R8, R10, and R11.

  R4, R7, or R8 will not send NLAs or Type 2 LSAs. These three routers are area border routers (ABR) for different OSPF areas. Like any other OSPF router, these routers generate Type 1 LSAs or router link advertisements (RLA). The LSAs

  contain the state of the routers that belong to same area. In this case, R4 generates and floods Type 1 LSAs into Area 0 and Area 10. Similarly, R7 and R8 flood Type 1 LSAs into Area 0 and Area 20, and Area 0 and Area 30, respectively.

  ABRs also generate Type 3 and Type 4 LSAs or summary link advertisements (SLA). These LSAs are flooded into other areas to and from the backbone area. Type 3 LSAs contain the list of networks that are exchanged between two areas.

  In this case, R4 floods Type 3 LSAs into Area 0 and Area 10; R7 floods these LSAs into Area 0 and Area 20; and R8 floods them into Area 0 and Area 30. Type 4 LSAs list the routes that point to autonomous system boundary router (ASBR).

  R13 will not generate Type 2 LSAs. R13 is an Area System Border Router (ASBR), which generate Type 5 LSAs apart from Type 1 LSAs. Type 5 LSAs, or external link advertisements, list the routes external to the AS; they are flooded

  throughout the OSPF domain except for stub areas.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify network types, area types, and router types

  References:

  Cisco > Home > Support > Technology Support > IP > IP Routing > Technology Information > Technology Whitepaper > OSPF Design Guide

• Question 618:

  Based on the following partial output of the show ip ospf database command, which router roles(s) is Router7 performing? (Choose all that apply.)

  

  A. ABR

  B. ASBR

  C. BR

  D. IR

  Correct Answer: AC

  Router7 is an area border router (ABR) and a backbone router (BR). The output reveals the link state databases for two areas, area 0 and area 2. Only ABR routers will display multiple databases when you execute this command.

  If Router7 is an ABR, then it is also connected to the backbone and will be a backbone router.

  Router 7 is not an autonomous system boundary router (ASBR) because it only displays sections in the output for Type 1 and Type 2 link-state advertisements (LSAs). ASBRs will also have a section for Type 4 LSAs, which would have its

  own heading at the end of the output.

  Router7 is not an internal router. A router is either an internal router or an ABR and Router 7 is an ABR.

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify OSPF neighbor relationship and authentication

  References:

  Cisco > Cisco IOS IP Routing: OSPF Command Reference > show ip ospf database

• Question 619:

  

  Router R2 operates in a broadcast, multi-access network. Examine the following output of the show ip ospf neighbor command.

  Based on the output, with which routers can R2 establish a full adjacency?

  A. the neighbor at 192.168.5.6

  B. the neighbor at 192.168.5.10

  C. the neighbor at 192.168.5.116

  D. the neighbor at 192.168.5.107

  Correct Answer: D

  R2 can establish a full adjacency with the neighbor at 192.168.5.107 and the neighbor at 192.168.5.165. In a broadcast, multi-access network OSPF network, full adjacencies can only be established with a designated router (DR) or a backup

  designated router (BDR).

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify OSPF neighbor relationship and authentication

  References:

  Home.Support > Technology Support > IP > IP Routing > Design > Design Technotes > What does the show ip ospf neighbors command reveal? Cisco > Cisco IOS IP Routing: OSPF Command Reference > show ip ospf neighbor

• Question 620:

  RouterA and RouterB are both in OSPF area 2, and RouterA is connected directly to the backbone. Their router IDs are shown below:

  RouterA - 165.165.20.15 RouterB - 165.165.10.12

  Which commands should be executed on RouterA and RouterB to create a virtual link between the two routers?

  A. RouterA(config-router)# area 2 virtual-link 165.165.10.12 RouterB(config-router)# area 2 virtual-link 165.165.20.15

  B. RouterA(config-router)# area 2 virtual-link 165.165.10.12 RouterB(config-router)# area 0 virtual-link 165.165.20.15

  C. RouterA(config-router)# area 0 virtual-link 165.165.20.15 RouterB(config-router)# area 2 virtual-link 165.165.10.12

  D. RouterA(config-router)# area 0 virtual-link 165.165.10.12 RouterB(config-router)# area 0 virtual-link 165.165.20.15

  Correct Answer: A

  The area virtual-link command should specify the area to be traversed and the ID of the router to which the router being configured will connect. Therefore, the correct answer is:

  RouterA(config-router)# area 2 virtual-link 165.165.10.12

  RouterB(config-router)# area 2 virtual-link 165.165.20.15

  A virtual link is used to make a virtual connection of an area border router (ABR) to the backbone. It is used in situations where an area does not physically border the backbone area. The virtual link provides logical connectivity of the area to

  the backbone. If the virtual link appears not to be functional, which would manifest itself in Router A not having all of Router B's networks in its routing table, the state of the link can be verified on Router A by executing the show ip ospf virtual-

  link command. An example is shown below. The state of the link as shown in line 1 of the output should be up.

  RouterA# show ip ospf virtual-links

  Virtual Link to router 172.16.8.2 is up

  Transit area 0.0.0.1, via interface Ethernet0, Cost of using 10 Transmit Delay is 1 sec, State POINT_TO_POINT

  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 0:00:08

  Adjacency State FULL

  The configuration below is incorrect because area 0 is referenced in the second line. It should reference area 2, the area being traversed.

  RouterA(config-router)# area 2 virtual-link 165.165.10.12

  RouterB(config-router)# area 0 virtual-link 165.165.20.15

  The configuration below is incorrect because area 0 is referenced in the first line. It should reference area 2, the area being traversed.

  RouterA(config-router)# area 0 virtual-link 165.165.20.15

  RouterB(config-router)# area 2 virtual-link 165.165.10.12

  The configuration below is incorrect because area 0 is referenced in both lines. Both should reference area 2, the area being traversed.

  RouterA(config-router)# area 0 virtual-link 165.165.10.12

  RouterB(config-router)# area 0 virtual-link 165.165.20.15

  If the virtual link is incorrectly configured the following error will be generated:

  *Dec 10 00:31.146: %OSPF-4-ERRRCV: Received invalid packet mismatch area ID, from backbone area must be virtual link but not found from 165.165.10.5, Serial 0

  Objective:

  Layer 3 Technologies

  Sub-Objective:

  Configure and verify network types, area types, and router types

  References:

  Cisco > Home > Support > Technology Support > IP Routing > Design > Design Technotes > What Are OSPF Areas and Virtual Links?